1. Field of the Invention
The present invention relates to a cooling device which is used to reduce the temperature caused by heat generated, e.g., from a driver of a card type memory medium used in a personal computer, a digital camera, or the like, and to a method of producing the same. Moreover, the present invention relates to an electronic apparatus such as a personal computer, a digital camera, or the like, on which the cooling device is mounted.
2. Description of the Related Art
Storage media such as Memory Stick (registered trademark), Smart Media (registered trademark), Compact Flash (registered trademark), and so forth are small in size and thickness, and also the storage capacities can be considerably increased compared to conventional storage media such as Floppy (registered trademark) disks or the like. Thus, they have been generally used in electronic apparatuses such as personal computers, digital cameras, and so forth. Regarding some of these storage media, flash memories integrated with drivers are used, or drivers are mounted on the main parts of apparatuses, other cards, or the like. For the storage media, recently, the capacities have been significantly increased. With increasing of the storage capacities of the storage media as described above, problems have arisen in that much heat is generated to cause defects in operation.
Accordingly, it has been proposed that a cooling device is provided for a heat source in such an apparatus. For example, a cooling method using a heat pipe has been proposed.
A heat pipe is a metallic pipe of which the inner wall has a capillary structure, of which the inside is evacuated, and which tightly contains a small amount of water or a substitution Freon therein. When one end of the heat pipe is brought into contact with a heat source to be heated, the liquid contained therein is evaporated. Then, heat is taken into the gas as latent heat (evaporation heat). The heat is transferred to a low temperature region at a high speed (substantially equal to a sound velocity). The gas is cooled to be returned to the liquid, and the heat is released (the heat is released due to the condensation latent heat). The liquid is passed through the capillary structure (or due to the gravity) to be returned to its original position. Thus, the heat can be efficiently transferred.
However, the related art heat pipe is tubular and voluminous. Accordingly, the heat pipe is unsuitable as a cooling device for use in electronic apparatuses such as personal computers, digital cameras, and so forth for which reduction of the size and the thickness is required.
Accordingly, to reduce the size of the heat pipe, a cooling device has been proposed in which grooves are formed on the surface of a silicon substrate and that of a glass substrate to be joined to each other, and these substrates are joined to form the flow-path of a heat pipe between the substrates. When the joining is carried out, a small amount of water or a substitution Freon is introduced to be tightly kept. The phase of the water or Freon is changed in the heat pipe, so that the function of the heat pipe can be performed.
However, in the case in which the heat pipe is formed by use of a silicon substrate as described above, heat from an object to be cooled is diffused, since the thermal conductivity of the silicon itself is high. Thus, there are problems in that the evaporation of a liquid in the heat pipe is insufficient, or the evaporation is not caused at all, so that the function of the heat pipe can not be carried out.
Moreover, electronic apparatuses having silicone substrates mounted thereon have problems in that they may be broken in event that the apparatuses drop.